1. Field of the Invention
The present invention relates to an edge filter for a common rail fuel system and a fuel system incorporating an improved edge filter.
2. Background Art
Common rail fuel systems for high pressure fuel injection in internal combustion engines are used to filter contaminates, impurities and dirt upstream of the fuel injector. Common rail fuel injector systems may operate with pressure in the typical range of 20,000 to 32,000 psi. Injectors are connected to the common rail by high pressure tubing.
Common rail fuel systems utilize electronic controls to control the timing of the beginning of injection and the completion of injection. The timing of the injection cycle may be adjusted electronically. Maintaining high pressure in the system permits the accuracy of fuel injectors to be controlled within microns.
Edge filters are effective to filter particles in the fuel or particles created by machining of components and/or from the high pressure fuel flow. Edge filters are normally provided as the last component prior to the injector. Conventional cylindrical edge filters having flat leading and trailing ends are received in high-pressure connectors having a tapered entry surface in which a cylindrical edge filter is centrally fitted and received.
Prior art edge filters have a generally flat front face with V-shaped openings leading to a V-shaped channel. Fuel flows over the edge of the inlet slot into an outlet slot. The space between the inner diameter of the high-pressure connector and the edge formed between the inlet slot and outlet slot may be on the order of about 25xcexc to 35xcexc. Three inlet slots and three outlet slots may be provided in a spaced relationship about the edge filter.
Prior art edge filters when operating in the high pressure environment of the edge filter may develop standing pressure waves, stagnation or back flow eddies immediately upstream from the edge filter that are caused by the fuel encountering the planar face of the edge filter. Flow turbulence may also be created downstream of an edge filter that has a planar outlet end surface. Such flow disturbances may create a fuel flow restriction and may create pressure spikes that may adversely affect the life of the injector parts. Pressure spikes may create fatigue and vibration that can reduce the life of the injector parts.
Under ideal conditions pressure spikes are reduced and the flow of fuel through the edge filter should approach laminar flow that reduces fatigue and vibration by minimizing pressure spikes in the fuel injector. Increased pressure capacity and a reduction in disturbances of fluid flow are provided by the invention as summarized below.
According to the invention a contoured partially conical or partially spherical surface is provided at the leading end and/or trailing end of an edge filter to improve flow through the edge filter by eliminating flow restrictions at the leading end and/or trailing end of the edge filter.
According to the invention, an edge filter for a common rail fuel system is contoured on the inlet end of the edge filter to improve fluid flow upstream of the edge filter. The invention also relates to providing a non-planar surface on the outlet end of the edge filter into which the outlet slots open that is contoured to reduce turbulence in fuel downstream of the outlet end.
According to the invention, a pressurized fuel rail system having a fuel inlet tube defines a receptacle for an edge filter. The edge filter includes a body defining at least one inlet slot open to an inlet end and at least one outlet slot open to an outlet end. An edge is defined by a peripheral surface of the body between the inlet slot and the outlet slot. A filter slot is defined between the inner wall of the receptacle and the edge defined by the peripheral surface of the body. A non-planar surface is formed on the inlet end into which the inlet slot opens. The non-planar surface is contoured to reduce turbulence in fuel upstream of the inlet end.
According to another aspect of the invention, an edge filter having a body as previously described may have a non-planar surface formed on the outlet end into which the outlet slot opens that is contoured to reduce turbulence in fuel downstream of the outlet end.
According to other aspects of the invention, the contoured surface may be at least partially conical or, alternatively, may be at least partially spherical on the leading or trailing ends.
According to another feature of the present invention, the inlet slots and outlet slots preferably are sloped with the inlet slots in the direction of fuel flow being sloped 5% to 10% thereby decreasing the depth of the slot as it approaches the outlet end while the depth of the outlet slot increases at a slope of 5% to 10% as it approaches the outlet end. These slots are preferably V-shaped and are closed at the end opposite their respective faces into which they open. The edge filter of the present invention may have three inlet slots and outlet slots that are spaced apart 120xc2x0 around the circumference of the edge filter.
According to another aspect of the invention, an edge filter for a pressurized fuel rail system having a plurality of fuel injectors is provided through which pressurized fuel is fed to the injectors through a fuel inlet tube comprising a high pressure connector. The inlet and outlet ends of the edge filter are contoured to form a non-planar surface at both the inlet end and outlet end of the edge filter to reduce turbulence at both the inlet end and outlet end thereof.
These and other aspects of the invention will be better understood in view of the attached drawings and following detailed description of the invention.